Which nerve is not commonly used as a source of donor action in nerve transfer for treatment of brachial plexus injuries?
Hypoglossal nerve. Historically the hypoglossal nerve was used as a nerve transfer in brachial plexus palsy but it is not used in modern surgery. Fascicles from the median nerve and also the ulnar nerve are often used to innervate the motor branches to brachialis and biceps in the arm. Usually the fascicles of the ulnar nerve identified as innervating FCU are used to neurotise the motor branches to biceps (Oberlin’s transfer). Similarly, the flexor carpi radialis (FCR) fascicles from the median nerve can be used to neurotise the motor nerve to brachialis. Intercostal nerves are also a useful source of motor axons. The intercostal nerves can be transferred, if possible without nerve grafts, to the musculocutaneous nerve, the nerves to triceps, the thoracodorsal nerve or the long thoracic nerve. They can also be used to neurotise the motor nerves of muscles used in free muscle transfer.
The ‘safe’ position of splintage of the hand includes:
MCP joints flexed to approximately 60°. The safe position of splintage of any joint is that in which the maximum number of ligaments are at maximum tension (the ‘close packed’ position). The CAM shape of the metacarpal head produces maximum tension in the collateral ligaments in flexion. Flexion of the PIP joint produces folding of the proximal (flexible) part of the volar ligament, which rapidly contracts and a flexion contracture results. The DIP joint ligaments are maximally tense in extension. The safe position for splintage of the hand includes MCP joint flexion, with PIP and DIP joints in full extension.
Of the vascular organisation in the hand:
The collateral digital arteries in the finger arise from the superficial palmar arch. The superficial palmar arch, usually incomplete, is the direct continuation of the ulnar artery. In a minority of hands, this arch is completed by a contribution from a branch of the radial artery. It runs just deep to the palmar aponeurosis and gives off the collateral ‘true’ digital arteries. The deep palmar arch is more usually complete and is formed by the terminal branch of the radial artery and a contribution from the ulnar artery. It lies deep in the palm, immediately superficial to the metacarpals.
Of the major nerves in the forearm:
The anterior interosseous nerve runs on the interosseous membrane between flexor pollicis longus (FPL) and flexor digitorum profundus (FDP). The median nerve enters the forearm between the two heads of pronator teres. It ends by supplying the thenar muscles and the skin of the radial digits, including the pulps. The posterior interosseous nerve enters the extensor compartment between the two heads of supinator and ends by supplying the wrist joint, without cutaneous distribution. The anterior interosseous nerve leaves the median nerve in the proximal forearm and runs in the interosseous membrane between FPL and FDP, supplying both.
The carpal tunnel:
Is formed by proximal and distal carpal rows and the flexor retinaculum. It transmits the median nerve, and nine flexor tendons: the FPL and two to each long digit. The ulnar artery overlies the ulnar border of the flexor retinaculum, outside the carpal tunnel. The FCU travels outside the tunnel, inserting, via the pisiform bone, piso-hamate and piso-metacarpal ligaments into the ulnar carpus. The FCR lies in its own tunnel, in the groove beneath the ridge of trapezium, distinct from the main carpal tunnel cavity. Pressure in the carpal tunnel rises with each degree movement away from neutral (0°).